This invention relates to folding apparatus for paper products and more particularly to apparatus for folding freshly printed cut sheets of paper, whether single sheets or pre-folded "signatures", at very high throughput rates.
Automatic folding machines are used both in binderies to produce printed publications and in industries where it is necessary to fold cardboard. An important use for folding machines is in the production of envelope "inserts" for direct mail marketing. The known paper folding machines that are on press, however, operate at speeds that are relatively slow compared to the line speed of the printing press. The folding process is therefore often a limiting factor on the efficiency of the entire printing line, and therefore, off press finishing of inserts are most common. Typical speeds for such off press folding machines are 5,000-7,000 pieces per hour. Another important use is in the folding of "signatures", that is, printed cut sheets of paper that have already been folded. A typical signature is folded twice to form a four-ply product. In the production of many magazines, the quarter-folded signature is then chop folded in half to produce an eight-ply signature. A significant problem in known systems is that the quarter folding can be done at the speed of the printing machine, but the chop folding and any subsequent folding are done at a significantly slower speed.
Usually in known on-press folding machines, folds are made by mechanical means and twisted belts that engage the paper. In other paper folding machines, and in many cardboard folding machines, the fold is made by driving the paper against a stationary forming member. In either case, a significant problem heretofore has been that these machines are not only relatively slow, but also that there is sliding contacts between the paper and components of the machine that engage the paper. This sliding contact is very undesirable for printed paper products because it tends to mark the printed surface. This is a particularly difficult problem where the printed matter is to be fed directly from a printing press and the ink may not have fully dried. Thus, known folding machines are not suited for integration with the printing apparatus so that the folding can be accomplished as the material is printed and leaves the press.
Besides having a high throughput rate and an avoidance of smearing the printed material, a commercially acceptable folding machine should fold a product either in half or, for letter size inserts, in thirds. If it folds the product twice, ideally it should do so without using two machines or running the same product through the same machine twice. In known folding machines, for example, it is usually necessary to double run a letter size product in order to double fold the insert to a size that will fit a standard No. 10 size envelope (31/2 inches by 9 inches). A commercially acceptable folding machine should also operate reliably, maintain a proper alignment of the paper product during the folding, and accept a variety of product sizes and thicknesses, including multiple ply papers that have already been folded at least once.
It is therefore an object of this invention to provide apparatus and a method for folding single sheet and folded cut sheet paper products, and particularly freshly printed products, at very high throughput rates approaching 50,000 to 60,000 products per hour.
It is a further object of this invention to provide apparatus and a method for folding printed paper products without smearing or otherwise defacing the printed matter on the paper.
Another object is to produce a folding apparatus with the foregoing advantages that is also relatively free of paper jams and, if there is a paper jam, allows it to be cleared readily.
A further object of this invention is to provide a folding apparatus and method which can make one or two folds in a paper product with only one pass through the apparatus.
Still another object is to provide a folding apparatus with the foregoing advantages that can fold single or multiple plies of paper.
A further object of this invention is folding apparatus which is of relatively simple mechanical construction.